The present disclosure relates to a development device including an agitating/conveying member agitating/conveying two-component developer and an image forming apparatus including the development device.
In a development device visualizing an electrostatic latent image formed on a photosensitive drum to a toner image by using two-component developer consisting of a toner and a carrier, an agitating/conveying member agitating, frictionally charging and conveying the toner and carrier is provided.
Recently, a demand for space saving of an image forming apparatus is risen, and moreover, in a color multifunction peripheral and a color printer in a tandem type arranging a plurality of development devices in parallel, it is necessary to miniaturize the development device and to narrow a distance between the photosensitive drums. Thereupon, there is a development device having two agitating/conveying members disposed vertically to narrow the distance between the photosensitive drums.
In a case where the agitating/conveying members are disposed vertically, the developer is circulated between an upper conveyance chamber having an upper agitating/conveying member and a lower conveyance chamber having a lower agitating/conveying member. When the developer is drawn up from the lower conveyance chamber to the upper conveyance chamber, it is necessary to move the developer against gravity. As a feeding member drawing up the developer, a magnet roller connected coaxially to a developer carrier may be applied.
However, in a case where the magnet roller is connected coaxially to the developer carrier, a length in an axial direction of the developer carrier is lengthened and the development device is enlarged. Further, due to a complicated structure connecting the developer carrier and feeding member, cost increase is brought.
In a case where the agitating/conveying members are respectively arranged in the upper and lower conveyance chambers, a developer amount fed to the developer carrier is decreased in a communicating portion between the upper conveyance chamber and lower conveyance chamber. As a result, there are problems that a toner amount becomes insufficient and image density is lowered.
Because of this, the development device may be configured so that the agitating/conveying member and developer carrier is lengthened more than the photosensitive drum and image forming is carried out at a center part of the developer carrier except for the communicating portion. However, a length of the development device in an axial direction of the photosensitive drum is lengthened and the development device is enlarged.